This would be for my parents. They have mentioned they sometimes have problems hearing the dialogue from the TV speakers. Would be almost 100% TV listening through DirecTV. I understand the Pioneer's sound quality is probably better but would the 5.1 sound more than make up for it? Could the Vizio's center channel be turned up independent of the other channels for better dialogue clarity? Similar price ... what would you get?

This would be for my parents. They have mentioned they sometimes have problems hearing the dialogue from the TV speakers. Would be almost 100% TV listening through DirecTV. I understand the Pioneer's sound quality is probably better but would the 5.1 sound more than make up for it? Could the Vizio's center channel be turned up independent of the other channels for better dialogue clarity? Similar price ... what would you get?

I own an older Vizio with the voice optimization. It does very little in this regard and depends on the signal from your tuner to have the correlating data.

I also own the Pioneer which has the best iteration of a voice specific mode from any product that has passed through my home or that I have tested or assisted with set up in anyone else's home. Voice is clear and intelligible from my kitchen which is 55' from the TV/Speaker Bar. And that is with the volume at a reasonable level for listening from our sofa or love seat about 15' from the TV/Speaker Bar.